Canon has always been one step ahead of the pack when it comes to putting video in DSLRs. From the pro 5D to the beginner Rebel T's, it's been a leader. But the new tech in the Canon EOS 70D could change things forever once again.

The Canon EOS 70D uses a new 20.2-megapixel APS-C sensor. That spec might not sound all the remarkable from the outset, but the sensor's architecture is completely new, which allows the camera to achieve the fastest and most precise continuous autofocus while recording video. For many shooters, this is the holy grail. The killer feature they've been waiting for.

Let's back up. On the entry-level T4i last year, Canon started using a hybrid autofocus system that used a combination contrast and phase detection autofocus system so that the camera could focus continuously while recording video.

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When recording video, DSLRs use sensor-based autofocus, rather than the optical autofocus sensors that you use when you're simply shooting photos using through viewfinder. Initially, sensor-based systems were just too slow to work continuously because they only used contrast ratios to find focus. By sacrificing a couple of photodiodes on the sensor to phase detection, the new hybrid system was able to do the work of finding focus fast enough that it was reasonable to call it effective.

Or that was the theory anyway. We tested the system a couple fo different times on both the T4i and the mirrorless Canon EOS M, and we weren't blown away. It worked—yes—but it was still too slow to be reliable.

Now this year, the 70D introduces a new phase-detection only system Canon calls Dual Pixel CMOS AF. That sounds fancy, and actually, the tech behind it reflects a genuine advancement in technology rather than just a marketing gimmick. The new CMOS sensor's 20.2-megapixel resolution has been divided into 40.1 million-photodiode architecture so that you've basically got two diodes capturing light for each pixel.

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Why? Because now there is a phase detection diode at every point on the sensor. Instead of just a few scattered about, you've got a sensor evenly peppered with phase detection points. (The two diodes at each pixel point synthesize, so you're not losing light sensitivity—at least, that's what Canon tells us.)

In practice, this new AF system is pretty remarkable—at least as far as we can tell. We tried out a near-production version of the 70D at a briefing in New York, and the speed and precision of the autofocus during video was hard to believe. This video was made by Canon so it should be taken with a little bit of skepticism, but our brief experience with the 70D would seem to verify that some of this awesome is actually possible.

One of the nice things about the tech is that it gets rid of the old "focus hunt" that inches closer and closer to focus. Instead, the 70D's focus algorithms smoothly slide into place so you lose the jarring back-and-forth jumps you've noticed before.

The Canon EOS 70D swoops in above the Canon 60D in the line, although the 60D isn't going anywhere just yet. Similarly, Canon wanted us to be clear that it's not exactly a replacement for the 7D either.

The 70D offers a few improvements over its predecessors, including new articulating, three-inch capacitive touchscreen, and faster seven frame-per-second continuous shooting.

Amongst the drawbacks of the camera are that it doesn't have a headphone jack for monitoring the audio that you're recording through the mic jack or built-in microphone, which is sad, considering the strength of the camera's video features.

The camera will be available in September for $1200 (body alone), $1350 (w/18-55mm kit lens), and $1550 (w/18-135mm kit lens).